1. Field of the Invention
The present invention relates generally to powered machine tools and equipment, and more specifically to a modification for a Haas mill vertical milling machine, permitting considerably higher coolant pressures to be used and precluding or greatly reducing damage and wear to the carbide coolant seals within the machine.
2. Description of the Related Art
In commercial machine shops and related operations, the rate at which machining can be performed on a given workpiece obviously has a significant bearing upon productivity. High rates of machining, and correspondingly high productivity, are obviously desirable in such operations. Such machines are typically configured for rapid and efficient interchange of cutting elements or tooling, in order to minimize down time and increase productivity. An example of such is the Haas overhead milling machine, with its pneumatically operated tool unclamp mechanism, which drives the drawbar downwardly to release the tool holder from its tapered chuck or receptacle at the end of the spindle.
This system utilizes a relatively large diameter, short stroke plate which is driven downwardly by pneumatic pressure within a wide and relatively short cylinder. This plate engages a piston, with the piston contacting the upper end of the drawbar to drive the drawbar downwardly through the spindle. In such mills, the piston and drawbar are separated by a pair of coolant seal inserts, with the non-rotating piston seal insert contacting the drawbar seal insert during tool change and other operations.
The rate of machining of the workpiece is limited by several factors, such as the type and hardness of the material being machined, the specific machining operation, cutting speeds, tolerances and surface finish, etc. However, another limiting factor is the delivery of coolant to the workpiece as it is being machined. Automated powered machine tools and equipment almost universally provide for some form of coolant and/or lubricant to be delivered to the cutting element as it engages the workpiece being machined. Coolant can be delivered by an external coolant delivery system, or by manufacturing the machine with internal, through spindle coolant delivery passages. Where internal coolant delivery is provided, the coolant delivery passages and orifices are of fixed size in any given machine, and cannot be practicably enlarged for greater coolant flow. Thus, the limiting factor for coolant delivery is the pressure at which the coolant is being delivered.
Heretofore, coolant delivery in a conventional overhead milling machine has been limited to about 300 pounds per square inch (psi), with this limitation often being set by the internal seal inserts noted further above between the conventional non-rotating tool change piston and the upper end of the rotating drawbar to which the tool holder is removably secured. These inserts are customarily formed of an extremely hard carbide material, with their mating faces being machined to an extremely close tolerance. The mating faces of the two seal inserts are the only sealing means provided; no other elastomer or other seals are provided between the drawbar piston and the drawbar, to contain the coolant within the concentric drawbar passage.
This system has its disadvantages, in that the two inserts also suffer from impact forces when the piston is driven downwardly to force the drawbar down for tool holder release. The impact forces can cause the extremely hard and somewhat brittle carbide inserts to crack and chip, which leads to coolant leakage during operation of the mill. In a conventionally configured Haas mill, this coolant leakage often travels into the spindle bearings and washes out the lubricants therein, thereby ruining the bearings and requiring costly repair. Also, the conventional Haas mill seal inserts are in constant contact with one another, whether coolant is passing therethrough or not. When the mill is run without coolant, the friction between these seal inserts can produce considerable heat, which can deform the end of the drawbar and lead to further cracking and/or deformation of the seal inserts.
Accordingly, a need will be seen for a tool holder unclamp mechanism for a milling machine, particularly for the Haas mill type machine, which obviates the above problems. The present invention essentially comprises the incorporation of a rotary union at the upper portion of the tooling unclamp piston above the drawbar, with the union containing the seal inserts between the lower end of the piston and the upper end of the drawbar. The union permits relatively high coolant pressures to be run therethrough, and thus throughout the machine. The union includes means for separating the two seal inserts during periods where coolant is not being run through the system, thereby precluding frictional wear and heating of the two seal inserts against one another. The present invention also obviates impact forces between the two inserts during tool holder changes, by applying all compressive forces concentrically around the union, piston, and seal inserts to a collar or coupling which attaches to the upper end of the drawbar. When coolant is run through the system, any leakage from the seal inserts is contained within the union and thence passed from the machine, thereby protecting the spindle bearings of the mill. The present invention includes further advantages as well, such as tapering the walls of the pneumatically actuated center plate to preclude binding or xe2x80x9ccockingxe2x80x9d of the plate within its cylinder during tool changeover operations.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,481,248 issued on Dec. 2, 1969 to Donald F. Engstrom, titled xe2x80x9cDrawbar For Machine Tools,xe2x80x9d describes a tool unclamp drawbar assembly for a milling machine or the like. The Engstrom assembly utilizes pneumatic pressure both to extend and to retract the drawbar for tool release, using a concentric air impact motor for extending the drawbar and a radially displaced pneumatic motor for retracting the drawbar after a tool change. No disclosure is made of any form of concentric or other coolant passages through the machine, as provided in the mill incorporating the present invention. Moreover, the Engstrom system operates directly against the upper end of the drawbar, rather than applying tool holder release forces around the upper end of the drawbar, as in the present mechanism.
U.S. Pat. No. 3,678,801 issued on Jul. 25, 1972 to Robert Z. Hague et al., titled xe2x80x9cQuick Tool Change Mechanism For Machine Tools,xe2x80x9d describes a system utilizing a relatively wide, flat plate disposed within a mating cylinder concentrically above the drawbar of the machine. The plate includes a central xe2x80x9cboltxe2x80x9d having an open center, which fits over the upper end of the drawbar. When the plate is driven downwardly by pneumatic pressure, the xe2x80x9cboltxe2x80x9d contacts the end of the drawbar to drive it downwardly to release the tool holder at the lower end thereof. As in the Engstrom assembly discussed above, Hague et al. do not disclose any form of coolant passages in the machine incorporating their invention, and thus do not require any seal inserts, as incorporated in the mill to which the present invention is applied.
U.S. Pat. No. 4,063,488 issued on Dec. 20, 1977 to Franz Kagerer, titled xe2x80x9cTool Chuck,xe2x80x9d describes a clamping mechanism at the lower end of the drawbar, for clamping and unclamping the upper end of the tool holder within the lower end of the spindle. The Kagerer system has a series of radially disposed keys, which move radially from corresponding slots in the locking head to engage a flange extending from the stem at the upper end of the tool holder. This structure differs from that used with other mills, e.g. the Haas mill to which the present invention is applied, with the Haas mill having a series of ball bearings which engage cooperating receptacles in the locking head and stem of the tool holder. In any event, Kagerer does not disclose any means of actuating the drawbar or providing high pressure coolant through the drawbar and tool holder, as provided by the present invention.
U.S. Pat. No. 4,175,898 issued on Nov. 27, 1979 to Edward H. Wood, titled xe2x80x9cTool Changing Apparatus,xe2x80x9d describes a mechanism adaptable to a Bridgeport type mill, where the tool holder comprises a collet which is threaded to the lower end of the drawbar and keyed within the lower end of the spindle. The Wood mechanism drives the drawbar downwardly and simultaneously rotates the drawbar, to unscrew the collet from the lower end of the drawbar. The tool holder of the Haas machine, or similar machine to which the present invention is applied, is not threaded to the drawbar, and hence rotation of the drawbar is not desired during tool change. In any event, no disclosure is made of any form of coolant system in the mill of the Wood patent.
U.S. Pat. No. 4,290,720 issued on Sep. 22, 1981 to Roberto J. Ferreira, titled xe2x80x9cQuick Self-Release And Reload Tooling Device,xe2x80x9d describes a tool holder and clamping mechanism having a series of ball bearings which selectively lock into corresponding recesses in the sides of the stem of the tool holder or chuck.
This mechanism is similar to that used in securing the tool holder within a Haas mill. However, Ferreira does not provide a drawbar which continuously retains the tool holder within its tapered lower spindle end, as in the mill to which the present invention is applied. Rather, Ferreira uses a series of spherically ended rods to transmit compressive force to the stem of the tool holder or chuck. Ferreira does not provide any means of transmitting the compressive force around the upper end of the drawbar, as provided by the present invention, as the mechanism of the Ferreira patent does not include any central coolant passage or seals therefor.
U.S. Pat. No. 4,352,612 issued on Oct. 5, 1982 to Edmo Benatti, titled xe2x80x9cTool Fastening Device,xe2x80x9d describes a mill or similar machine in which the tool holder is secured in the lower end of the spindle by a series of vertically disposed fingers extending from the end of a compression rod which passes axially through the center of the drawbar. The fingers are splayed outwardly to grip the inside of the tool holder, when engaged. The installation of the locking rod within the drawbar precludes any coolant passages concentrically therethrough. Accordingly, there is no disclosure of any seals or circumferential transfer of tool holder release force around the seals, as in the present invention.
U.S. Pat. No. 4,884,899 issued on Dec. 5, 1989 to Everett H. Schwartzman, titled xe2x80x9cResiliently Mounted Fluid Bearing Assembly,xe2x80x9d describes a hydrostatically or hydrodynamically supported spindle for high speed operations, i. e., in excess of 100,000 rpm, according to the abstract. No coolant passage for tooling is provided through the central shaft of the device, in any of its embodiments. As the Schwartzman device is intended for considerably higher rotational speeds than used in a milling machine or the like, it is not adaptable to a Haas mill or other similar mill. Accordingly, no tool holder or means of releasing such a tool holder, is disclosed by Schwartzman in his patent.
U.S. Pat. No. 4,957,398 issued on Sep. 18, 1990 to Manfred Schneider et al., titled xe2x80x9cTwo-Section Tool Spindle Having A Channel For Carrying A Pressurized Fluid,xe2x80x9d describes a mechanized tool spindle having an electric motor disposed generally centrally along the length of the spindle. The spindle includes an xe2x80x9coperating rodxe2x80x9d disposed concentrically therein, with the rod acting as the drawbar in the mill of the present invention. Axial movement of the rod is provided by a piston and cylinder, but the cylinder drives a hollow rod which is in turn threaded to the operating rod. As the two rods are essentially permanently connected to one another, Schneider et al. do not provide any mating seals therebetween. Thus, the tool holder release force acts through the operating and connecting rods, rather than around these components to protect the seal inserts, as would be the case in the mill of the present invention.
U.S. Pat. No. 4,976,282 issued on Dec. 11, 1990 to Zbignew Kubala, titled xe2x80x9cCoolant Union With Fluid Actuated Seal Assembly,xe2x80x9d describes a fluid joint having a relatively stationary outer shell communicating internally with a rotary shaft extending from one end thereof. The Kubala patent has been assigned to the Deublin Company, which manufactures the device, with the device being known generally as a xe2x80x9cDeublin union.xe2x80x9d The structure of the Deublin union of the Kubala ""282 U.S. Patent is incorporated herein by reference. The Deublin union includes non-rotating and rotating seal inserts used between the upper end of the drawbar and the piston to drive the drawbar downwardly in a Haas mill or similar machine. However, the Deublin union of the Kubala ""282 U.S. Patent includes a resilient diaphragm which draws the non-rotating seal away from the rotating seal, when coolant fluid pressure is not present. Thus, the only time the two seals are in contact with one another, is when coolant is being forced through the union. It will be noted that some coolant will escape from between the two seal inserts, particularly when coolant flow is initiated and when flow is terminated. Accordingly, a radially disposed coolant relief passage is provided in the side of the Deublin union, to allow coolant to escape therefrom without contaminating the spindle bearings, with a seal provided between the coolant escape cavity and bearings. While such Deublin unions are known, they have not been incorporated with a mill of the Haas mill configuration prior to the present invention, with the present mechanism using such a Deublin union therewith.
U.S. Pat. No. 5,022,686 issued on Jun. 11, 1991 to Helmut Heel et al., titled xe2x80x9cRotating Union For Two Different Fluids,xe2x80x9d describes a device having two separate fluid passages therethrough. One passage is concentric, with the other being radially offset therefrom and parallel thereto. A pair of xe2x80x9cslide rings,xe2x80x9d which appear to function much the same as the seal inserts used in the conventional Haas mill and Deublin union, are provided within the union of the Heel et al. patent. However, no means is apparent for separating these two seals when no fluid is passing through the union, unlike the Deublin union described further above with its selectively engageable seals. In any event, Heel et al. do not disclose any means of providing drawbar compressive force around their union, as provided by the present invention.
U.S. Pat. No. 5,340,248 issued on Aug. 23, 1994 to Bernhard Enbergs, titled xe2x80x9cMechanical Chuck With Clamp For Pulling Tool Shank To Tightly Clamped Position,xe2x80x9d describes a chuck or tool holder mechanism wherein the pull rod (drawbar) does not pass completely through the machine to have tensile force applied to the end opposite the tool holder in order to hold the tool holder in place. Rather, the Enbergs mechanism provides a relatively short, flanged tool holder, with a series of pins in a generally conical array being forced against the tool holder flange by a nut when the nut is tightened. Accordingly, no coolant passage is provided through a drawbar which extends through the machine, as in the present invention. Accordingly, Enbergs does not disclose any seal inserts or means for displacing operating forces around such inserts.
U.S. Pat. No. 5,577,775 issued on Nov. 26, 1996 to Dennis G. Pearson et al., titled xe2x80x9cBearingless Coolant Union,xe2x80x9d describes a union incorporating a stationary and a rotating seal insert, with the two seal inserts bearing against one another, generally as disclosed in the device of the Kubala ""282 patent discussed further above. More particularly, Pearson et al. state that their seals are xe2x80x9cin permanently contacting relationxe2x80x9d (col. 5, line 45) with one another, as in the union of FIG. 1 of Kubala, noted in that patent as prior art. The disadvantages of permanently engaged seal members have been noted further above, and in any event, Pearson et al. make no disclosure of any means of applying a compressive force to a drawbar by structure bypassing the seals within the union, as provided by the present invention.
U.S. Pat. No. 5,617,879 issued on Apr. 8, 1997 to Zbignew Kubala, titled xe2x80x9cSealing Arrangement For A Coolant Union Having A Floating Seal Assembly,xe2x80x9d describes a union loosely related to the union of the ""282 U.S. Patent to the same inventor, discussed further above. The device of the ""879 patent differs primarily in that the force for separating the two seals when no coolant pressure is present, is supplied by a spring which applies constant pressure to the non-rotating seal at all times. Otherwise, the same points raised in the discussion further above of the Deublin union of the ""282 U.S. Patent, i. e., the lack of incorporation of such a union with a Haas or similar mill, are seen to apply here as well.
U.S. Pat. No. 5,669,636 issued on Sep. 23, 1997 to Zbignew Kubala, titled xe2x80x9cFloating Seal Assembly For A Bearingless Coolant Union Having Air Rotation Capability,xe2x80x9d describes a union which closely resembles the union of the ""879 U.S. Patent to the same inventor, discussed immediately above. However, the union of the ""636 patent includes a radial port and circumferential chamber for applying air or liquid pressure thereto for balancing the force of corresponding air or liquid applied through a concentric port to the union. A spring is provided to separate the two carbide seals within the union at such times that no pressurized fluid is being applied to the device. As in the other two patents to Kubala discussed further above, no disclosure is made of the adaption of the union to a Haas or similar mill, and in fact the disclosures of the ""879 and ""636 Kubala patents teach away from such an application by illustrating the union with a completely different type of equipment.
U.S. Pat. No. 5,743,687 issued on Apr. 28, 1998 to John Ribic et al., titled xe2x80x9cFourth Axis Fixture Quick Change,xe2x80x9d describes a device including a concentric union for transmitting pneumatic pressure to a wide, short piston and cylinder assembly for controlling axial movement of a drawbar. No coolant passage is provided through the drawbar, as the pneumatic line connects concentrically with the top of the cylinder. Moreover, the piston transmits its force directly to the drawbar, with no means for applying the force peripherally about any intervening structure, such as the Deublin union used with the present invention.
U.S. Pat. No. 5,901,643 issued on May 11, 1999 to John B. Bornhorst, titled xe2x80x9cHigh Pressure Rotary Union For Mechanical Power Press,xe2x80x9d describes a rotary joint for supplying high pressure hydraulic fluid or the like from a stationary supply to a rotary shaft. The Bornhorst union is considerably simplified relative to the Deublin union and pneumatically actuated, axially operable drawbar release piston of the present invention, as the Bornhorst device is not required to provide any form of axial movement or to accommodate such axial movement along a shaft.
U.S. Pat. No. 6,029,695 issued on Feb. 29, 2000 to Michael Logan, titled xe2x80x9cRotary Union For Transmitting A High Pressure Medium,xe2x80x9d describes an assembly having a concentric fluid passage therethrough. The Logan union includes a series of circumferential bearings and bleed passages allowing fluid bypassing the internal seals to escape without damaging the bearings. However, the Logan union does not provide any means for transmitting axial motion therethrough, and accordingly does not contain facing seals of carbide or any other material. Moreover, no disclosure is made of the adaption of the Logan union to a Haas or similar mill, nor of any means for transferring axial motion peripherally about the union to avoid damage to facing seals therein, as provided by the present invention.
U.S. Pat. No. 6,109,659 issued on Aug. 29, 2000 to David C. Heidenreich et al., titled xe2x80x9cHydrostatic Rotary Union,xe2x80x9d describes a fitting having a rotary component captured within a relatively stationary housing, by an end cap threaded onto the housing. The rotary component is axially immovable within the housing, and thus has no facing seals therein. Heidenreich et al. make no disclosure of any adaption of their union with a Haas mill or similar machine, nor do they disclose any additional structure for transmitting axial motion about their union, as provided by the present invention.
Canadian Patent No. 598,285 issued on May 17, 1960 to Hallis N. Stephan, titled xe2x80x9cHorizontal Boring, Drilling, And Milling Machine,xe2x80x9d describes a machine having a tool holder which is secured within a taper in the end of the spindle by a drawbar applying tensile force thereto, as is conventional in the art and generally disclosed in the ""248, ""801, ""488, etc. U.S. Patents discussed further above. As in the case of those U.S. Patents, the ""285 Canadian Patent does not disclose any means for supplying coolant axially down the center of the drawbar and tool holder. Also, as no axial coolant is provided, no fluid union or adapter is disclosed, and hence no means is provided for applying a drawbar release force peripherally about such a union, as provided by the present invention.
British Patent Publication No. 859,457 published on Jan. 25, 1961 to Worcester Valve Co., Inc., titled xe2x80x9cA Rotary Ball Valve And Union Having A Detachable End Fitting,xe2x80x9d describes a device serving as a combination of a shutoff valve and union, thereby saving space in the installation. The Worcester Valve device is unrelated to any fluid unions adaptable to the present invention and its installation with a Haas mill or related device, as the Worcester Valve cannot transmit rotary motion thereacross.
Moreover, no means is disclosed for transmitting axial motion around the valve, which means is a part of the present invention.
Finally, Soviet Patent Publication No. 1,579,653 published on Jul. 23, 1990 describes (according to the English abstract and drawings) a hydraulically actuated drawbar release mechanism, wherein hydraulic pressure is applied concentrically to the end of the drawbar and spindle housing. This applies pressure to a concentric piston, which compresses the Belleville washer stack within the spindle to push the drawbar downwardly to release the tool holder. Most of this structure is conventional, and used in the Haas and other mills to which the present invention is applied. However, no disclosure is made in the Soviet Patent Publication of any coolant passage through the drawbar and tool holder, nor of any means for applying drawbar release pressure around the concentric hydraulic fitting, which means are a part of the present invention.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed.
The present invention comprises a mechanism for releasing or unclamping a tool holder in a machine tool, by releasing the tensile or retractile force on a drawbar which secures the tool holder within the mating internally tapered end of the spindle of the machine. The present invention is particularly well suited for adaption to Haas mills, which conventionally use a relatively large diameter and short stroke plate acting within a pneumatic cylinder to drive a piston downwardly against the top of the drawbar, thereby compressing the drawbar retraction springs to extend the drawbar and allow removal of the tool holder from the opposite end thereof.
Such a conventional mechanism may include an external or internal system for supplying coolant to the tool and workpiece interface, for cooling and lubricating the cutting action for more efficient operation. Where an integral, internal coolant supply system is used, the coolant is piped concentrically downwardly from a connector at the upper end of the drawbar, through the drawbar and tool holder, and to the tool held in the tool holder or sprayed from the tool holder onto the area of the cutting edge of the tool. A non-rotating seal is affixed to the lower end of a non-rotating stem at the upper end of the drawbar, with a rotating seal affixed to the upper end of the rotating drawbar. These two seals are formed of an extremely hard carbide material, in order to resist wear as they bear against one another during machining operations.
The problem with such a conventional system is that when the pneumatic system is actuated to drive the drawbar downwardly for tool holder release, the impact force is applied directly across the two carbide seals. This tends to deform and crack the seals, whereupon they are subject to leaking of coolant during subsequent machining operations. The leaked coolant often migrates past seals and other barriers, and enters the upper bearings for the drawbar. The improper lubrication provided by the coolant causes the bearings to become damaged, thus requiring relatively time consuming and costly repair of the machine. Moreover, the two seals conventionally bear against one another at all times. This is not particularly harmful when coolant is being pumped through the concentric coolant passage of the drawbar, as some coolant will interpose itself between the non-rotating and rotating seals to preclude, or greatly reduce, wear and frictional heating. However, the seals are subject to deformation and other damage due to overheating, when coolant is not used during machining operations.
The present invention responds to the above problems by integrating a Deublin union as the coolant supply union for a Haas mill or similar machine. Such Deublin unions include the non-rotating and rotating seals therein, and include means for separating the two seals when no coolant pressure (and therefore no coolant) is being provided. Moreover, the present invention includes a mechanism for imparting the drawbar release forces peripherally around the Deublin union and its internal seals, thereby precluding the application of force to the seals therein.
Accordingly, it is a principal object of the invention to integrate a Deublin union with the upper end of the drawbar actuation piston of a Haas mill or similar machine, thereby utilizing the seals internal to the union and removing other seals between the drawbar and piston.
It is another object of the invention to provide a drawbar actuation mechanism comprising a pneumatically actuated mechanism disposed peripherally about the Deublin union, thereby precluding application of compressive or impact forces axially through the Deublin union and its internal seals.
It is a further object of the invention to seal the Deublin union to the upper end of the drawbar by means of a positive coupling, thereby precluding leakage of coolant into the spindle bearings of the machine. Still another object of the invention is to provide a pneumatically actuated piston plate for extending the drawbar, with the piston plate having a circumference with a conically tapered section for precluding jamming and sticking of the piston plate within its pneumatic cylinder.
It is an object of the invention to provide improved elements and arrangements thereof for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.